I'm still early in my career, but the last two rounds of interviews I've done have yielded initial offers with a spread of $100k+/yr in total comp and $60k+/yr in base salary.
Just to have concrete numbers to work with, suppose initial offers exactly correspond to final pay and that you're currently making toward the lower end of that range (e.g. because raises haven't kept up with your increased skill and increased market demand).
If you're currently making $X/yr (total comp), you think you _might_ be worth $X+$50k to somebody, and you spit out $X+$50k as your target range, a prospective employer could generously offer $X+$60k and you'd be happy as a clam and none the wiser while missing out on a new Tesla per year in extra pay.
There's a separate argument that if you'd be happy with $X+$60k then you shouldn't try to squeeze your employer for more, but I'll let somebody else make it if they'd like. Regardless, that big of a spread really does exist, and I imagine it grows further into one's career.